Electron tube



May 16, 1950 F, L D, 2,508,280

ELECTRON TUBE Filed March 17, 1945 {Sheets-Sheet 1 May 16, 1950 F. LUDI 2,508,280

ELECTRON TUBE Filed March 17, 1945 v r 2 Sheets-Sheet 2 z; I W;

III

INVEN TOR.

Patented May 16, 1950 ritz- -11 Liidhfiaden,Switzerland, assignor to Patch (1 Patentverwertungs- & Elektro- Holding AL-G Glarus, Switzerland Arr ionM rchl ,.2 r aLN 3.22 InSwitzerland February. 1, 19,49...

Se fimthltnb Law 690,. l s' t' 1 6 Patent expires February '1, 1 964 15 Claims. .(01. 250-2715 Thepresent inventionconcerns electron tubes fonultra short electromagnetic oscillations which have at least a cathode, an anode consisting of segments --biased positively with respect to the.

cat hode-,- a-nd-a magnetic field, there being a high frequency alternating; voltage between neighboure anode segments, and where according to the invention at-a distancewhich is. approximately constantdrom the anode a guide electrode is providedwhich-at least over its greatest par-tis not penetrated by the electrons, the electrons following-paths between theguide electrode and the anode.

I-n -the--ultra short electric wave range three fundamentally different-kinds oftube types are known, namely retarding field tubes, magnetron tubes and the K lystron. The tube according to the invention is on account ofits method of operation comparable withtransit time tubes with density-modulated electron beams, but still more so with magnetron tubes. Nevertheless when compared with such tubes there are very pronounced and important differences so that it forms 'a fundamentally new tubetype for the ultra short wave range.

The method of operation of the tube is such that the electrons emitted from the cathode pass to a space bounded by the auxiliary electrode and the anode where they are subjected tothe alternating field prevailing between the anode se ments, the constant field existingbetween the anode and the-cathode-or guide-electrode, and tothe applied magnetic'field. The electrons move underthe infi uenceof' these fields along paths between the anode and the guideelectrode. The

alternat-ingfield-at theanode segments causes velocity--modulation of the electrons which as these latter move onwards changes into a density ueta he.ele. tme. ndn s iiveiont ruditean id amedhedmnta e. s. a ided.v w ube. becausedue to heirn ssins b tween t e ide elec ro e. endur ancde h e ectr ns o ot. r tur o. he im ediat icinit o e ot athode. afte ach. sc l ation. ndQthe os tive ns; mcst ye en. bath au i i ry ect ode -fl stead of on the hot cathode. The pathof the electrons: from-the cathode to. the anode, can have any length. Furthermore the size of thetube for oscillations in the centimetre. wave range is .not

unfavcurablysmall. Finally an optimum efiiciency is reached which is. notexceeded by, a mag: netron tube.

A number of constructionalexamples of the in- Vention are illustrated in the accompanying drawing, Figs. 1 and. 2 showing theessential ele-.

ments of a tube. in perspective viewand crosssection respectively, Figs; 3-6 show various constructional formsof the cathode. and guide electrode in section, Fig. '7 is.a substantiallyaxial sectionthrough an electron tube. embodying the invention, the section beingtaken on the plane of line 'I'-'I of FigrBg'Fig. 8 is a transverse section through the same. on theplane of section line 878 of Fig. '7'; and Fig- 9 is.a perspec eview of another embodiment-of the inventQ-n.

In Fig. 1a cavity resonator assembly for atube of cylindricalv designis shown, I being the electron-emitting hot cathode, 2 a guide electrode and: I. I va cavity resonator at anode-potential. The resonator I I isbounded by the outer cover 3, two end walls land by the anode segments 5. There is also a magnetic field in the. direction of the axisfi which is indicated in Fig. 2 by the pole pieces N and S. Guide-electrode 2 has the same potential as cathode I so that there is a cavity resonator assembly for a constant electrical field which is directed outwards.

During operation the electrons emitted from cathode I travel under the influence of the radial electrical and axial magnetic field along cycloidal pathsbetweenthe guide electrode 2 and the anode segments 5- in the circumferential direction of the micro-wave tube. When resonator I! oscillates, opposed positive and negativecharges occur alternately between neighboring segments 5, which represent the capacity of the 'cavity resonator. so that a high frequency alternating field exists beeen h s s ments T i a t rn tin l messes. a ly t enrthe v l cit o h e rons vary, hereup n th l r ns as he e n rd 3 .bllI fih s l P- hi ria iqn ind esi y. n. t r result n. ncr as f th hi h frqq enc l srn tins fiel be e the anode segments, so that the oscillations become stronger. The electron bunches which have given up th'eir energy, finally reach theano'de.

Generally practically all the electrons after a complete revolutionabout the axis of the electron tube will either beabsorbedby the uide electrode orwill have removed. themselves far away from this electrode, so that no more can reach the hot cathode l and thus there will be no return heating from the electrons, such as otherwise occurs in magnetron tubes. Also the return heating by positive ions which may exist as a result of the residual gas is practically negligible, because these ions are completely caught by the guide electrode 2.

The efficiency of the tube is determined by the relationship between the width of the anode segments and the distance of these latter from the guide electrode, and the wave length of the generated oscillations is at a first approximation a function of the mutual capacitance of the anode segments per unit of length in the circumferential direction, of the distance of segments from casing 3 in Fig. l, and of the axial length of the cavity resonator. Since also constructional aspects play a part in the dimensioning of the segments, the number of such segments can vary very greatly in different tubes. The number of segments and thus the power of the tube can for the same wave length be increased almost indefinitely. This is a fundamental advantage of the tube according to the invention when compared with known types of micro-wave generators.

Another constructional example of the invention is illustrated in Fig. 2 in cross-section. The same reference numerals are used as in Fig. 1. In this case the cathode is constructed as a spiral. Furthermore end plates 1 are provided which are galvanically .connected with the auxiliary electrode 2 for the purpose of preventing high frequency power radiation losses and an undesirable diversion of the electrons. A conductive loop 8 is provided for power collection.

The construction of the cathode and guide electrode is important. Various constructional forms of these elements are illustrated diagrammatically in Figs 3-6, where I again represents the cathode. In Fig. 3 guide electrode 2 encloses the cathode at the side furthest away from the anode and is thus fully closed in the circumferential direction. In Figs. 4 and 5 a control electrode is provided which is preferably given a negative potential relative to the guide electrode. The control electrode may be a strip 9 located inwardly of the cathode l, as in Fig. 4, or may be a channel member 9 with flanges at opposite sides of the cathode, as in Fig. 5. The control electrode can be made like a Wehnelt cylinder. When, as shown in Fig. 6, the guide electrode 2 has turned-in edges In, it is advisable to give cathode l a negative bias relative to electrode 2". The guide electrode or electrodes 2a can also be so formed that in the vicinity of cathode l or control electrode 9, the cathode does not lie in the plane of guide electrode 2a but slightly outside of it. Control electrodes 9 can be given a constant or variable potential. The voltage between cathode and guide electrode can also be variable.

A constructional embodiment of the invention, and of the plural cathode, plural guide electrode type of Fig. 4, with four cathodes II and four guide electrodes I2, is illustrated in Figs. 7 and 8.'

The cavity resonator is provided by an outer cyllindrical wall 13 which extends beyond the annular walls M on which the anode segments l5 are mounted in alternation. The wall l3 forms a part of the envelope of the tube and its opposite edges are sealed into glass or ceramic rings [6, l7 into which cup-shaped end closures I 8, l9

of non-magnetic metal are sealed. The wall I3 I is provided with a slot 20 through which a coupling loop 8 extends into the cavity resonator, and the continuity of the evacuated envelope is preserved by a tube or sleeve 2| which surrounds the loop leads and is soldered or welded to the cylindrical Wall l3, the outer end of the tube 2| being closed by a glass or ceramic dome 22 in which the loop is sealed.

The cathodes I I are of spiral type each having one terminal connected to a disk or spider 23 on a lead-in rod 24 which extends through a glass or ceramic dome 25 closing the inner end of a metal tube or sleeve 26 which is soldered or otherwise sealed to the end closure 59. The other end of each cathode H is soldered to a cup or spider 21 which is secured to the end closure l9 by screws 28. The guide electrodes l2 are soldered or welded to a cup-shaped support 29 which is secured to the other end closure I8 of the envelope by screws 30.

In another embodiment of the invention, as shown in Fig. 9, a cavity resonator H as illustrated in Fig. 1, is supported within an evacuated glass envelope 3% by a lead-in wire 32 and metal strap 33. The cathode rod l is supported eccentrically of the resonator axis by metal straps 34 which extend through and are sealed in the glass press 35. A control electrode 9 is supported adjacent the cathode by its lead-in wire or rod 36 and the cylindrical guide electrode 2 is mounted on and supported by its lead-in wire or rod 31. Terminal wires are connected to the several leadin wires or straps for applying energizing potentials to the several electrodes, and the direct current potential on the guide electrode may be the same as or different from the cathode potential.

The cathode can be a spiral or in the form of a hot filament or large surface cathode; it can be heated directly or indirectly. It consists either of one, or with high power tubes, Of several filaments or spiral-shaped emitting cathode conductors which are arranged directly next to or along the circumference of the guide electrode,

Its shape can, however, difier considerably from those shown in the drawing. In certain cases a Lecher wire can also be used to advantage for the oscillations.

Those elements which are subjected to heat stresses can for instance be cooled by radiation by painting them black. Their surfaces can also be enlarged by cooling fins. Particularly with high-power tubes it is advisable to provide water cooling. For those parts which are especialy subject to heat stresses a special heat-resistant material, for instance tantalum, is used.

The natural frequency can be varied by altering the volume of the cavity resonator. This can also be achieved by varying the penetration of field displacing means at the point where there is a large magnetic or electric energy, or the capacity of the resonator can for instance be varied by varying the mutual capacity of the anode segments. Another possibility for varying the frequency is to change the tuning of a Lecher line which is coupled to the resonator. Finally the strength of the magnetic field, or the anode voltage, or both, can be made variable for certain purposes.

I claim:

1. An electron tube for ultra high frequency electromagnetic oscillations comprising, within a tube envelope, a hollow cavity resonator having inner and outer cylindrical walls connected by end walls, the inner cylindrical wall being divided by a zig-zag' slot into a plurality of pairs of parallel anode segments connected in alternation to the respective end walls, a cathode extending 1on gitudinally 0f the cylindrical space defined by said anode segments and supported eccentrically of the axis of said cylindrical space, guide electrode means having a circumferential gap in which said cathode is located and spaced at a substantially constant radial distance from said anode segments to define therewith an annular space within which electrons emitted by said cathode may travel, said cavity resonator and anode segments being adapted to be positively biased with respect to said cathode and guide electrode means, said guide electrode means comprising a cylindrical electrode having a circumferential length in excess of the circumferential length of a plurality of adjacent anode segments, and means external to said tube envelope to establish a magnetic field Within and parallel to said cylindrical assembly of anode segments.

2. An electron tube as recited in claim 1, wherein said guide electrode means comprises a single cylindrical surface coaxial with the cylindrical assembly of anode segments and with longitudinal edges terminating adjacent said cathode.

3. An electron tube for ultra high frequency electromagnetic oscillations comprising, within a tube envelope, an electron-emitting cathode a hollow cavity resonator having as an inner cylindrical wall, an anode comprising a plurality of pairs of parallel segments adapted to be biased positively with respect to said cathode, said segments being a cylindrical assembly and said cathode being positioned eccentrically of said cylindrical assembly, and a guide electrode comprising a cylindrical portion coaxial with said cylindrical assembly of anode segments, the ends of the cylindrical portion terminating adjacent said cathode.

4. An electron tube as recited in claim 3, wherein an integral portion of the guide electrode connects the ends of said cylindrical portion and is located inwardly of said cathode.

5. An electron tube as recited in claim 3, wherein radial flanges extend inwardly from the ends of the cylindrical portion of said guide electrode.

6. An electron tube as recited in claim 3, wherein electrode means is arranged at the side of said cathode opposite the anode segments adjacent thereto.

7. An electron tube as recited in claim 3, wherein a control electrode is arranged at the side of said cathode opposite the anode segments adjacent thereto.

8. An electron tube as recited in claim 3, wherein a control electrode is arranged at the side of said cathode opposite the anode segments adjacent thereto; said control electrode having radial flanges extending to opposite sides of, and in spaced relation to, said cathode.

9. An electron tube comprising a plurality of electron-emitting cathodes, a plurality of pairs of anode segments substantially parallel to said cathodes in a cylindrical assembly and adapted to be biased positively with respect to said cathodes, said cathodes being spaced along and equidistant from the surface defined by said anode segments, and guide electrode means spaced substantially uniformly from said anode segments in the circumferential gaps between adjacent cathodes and forming with said anode segments a path for electrons emitted by said cathodes, the

; number of cathodes and guide electrode means being substantially less than the number of pairs of anode segments.

10. An electron tube as recited in claim 9, wherein said anode segments are arranged in a cylindrical assembly, said cathodes are positioned eccentrically with respect to said cylindrical assembly, and said guide electrode means include a plurality of cylindrical portions coaxial with said cylindrical assembly of anode segments.

11. An electron tube as recited in claim 9, in combination with electrode means located radially inwardly of the several cathodes.

12. An electron tube as recited in claim 9, wherein said anode segments constitute a portion of a cavity resonator.

13. An electron tube as recited in claim 9, in combination with lateral plates electrically connected to said guide electrode means to limit the electron path, said plates being perpendicular to the magnetic field.

14. An electron tube as recited in claim 3, in combination with lateral plates electrically connected to said guide electrode to limit the electron path, said plates being perpendicular to the magnetic field.

15. An electron tube as recited in claim 3, in combination with lateral plates of annular form electrically connected to said guide electrode to limit the electron path, said plates being perpendicular to the magnetic field.

FRITZ LiiDI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Great Britain July 11, 1939 Number Number Certificate of Correction Patent No. 2,508,280 May 16, 1950 FRITZ LUDI It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correction as follows:

Column 6, line 31, for the claim reference numeral 9 read 1;

and that the said Letters Patent should be read Withthis correction therein that the same may conform to the recordof the case in the Patent Office. a Signed and sealed this 8th day of August, A. D. 1950.

THOMAS F. MURPHY,

Assistdnt Commissioner of Patents. 

